Secondary sexual characteristics in codfishes (Gadidae) in relation to sound production, habitat use and social behaviour

• Main Authors: Skjaeraasen, J.E., Meager, J.J., Heino, M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Taylor & Francis 2012
• Subjects: Gadus morhua
• Online Access: http://pure.iiasa.ac.at/id/eprint/9978/

Little is known about the reproductive biology of the codfishes (Gadidae). Lacking direct observation, the study of secondary sexual characteristics can provide cues to their reproductive biology and behaviour. We reviewed here published accounts on sexual dimorphisms in 25 gadids in light of their general lifestyle, i.e. pelagic or demersal, and social behaviour. In addition, complementary data on fin lengths and drumming muscle size in haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), blue whiting (Micromesistius poutassou) and cod (Gadus morhua) are presented. Capacity for sound production occurred in almost half of the studied species, but was most prevalent in demersal species, where it is probably used in resource contests and to attract mates. For semi-pelagic gadids, we postulate that sound production may be lined to the formation of male-biased spawning shoals and the attraction of females towards such shoals; we identify candidate species to further test this hypothesis. Although rarely studied, sexual fin dimorphisms occur in several gadids. Cod, saithe and blue whiting males have longer pelvic fins than females, whereas no such dimorphism was observed in haddock. In cod and haddock, males use pelvic fins during courtship of females and agonistic encounters with other males. Pelvic fins probably also have a similar function in other gadids. The hitherto available information on sexually dimorphic traits and/or courtship behaviour in seven gadid species suggests that complex mating systems and non-random mate choice occurs frequently in this important goup of exploited fishes.